SOIL SURVEYS

A soil survey shows the kinds of soil that exist
in a given region and their exact location on a
map of the landscape. Names are assigned to
soils at these locations in accordance with
properties they do or do not possess. Over
time all soil surveys monitor changes in the
soils as they are altered through agriculture
and other types of land use. The surveys also
help to predict the success of any use to which
the land is put. If used to their potential, soil
surveys indicate how long the soil can sustain
current practices.

Names are assigned to soils through development
and application of a system of classification.
Soil surveys in the United States have
been developed using several classification
schemes, with the first being merely a map of
the surficial geologic deposits. C. F. Marbut's
classification system was put into use in the
early part of the twentieth century. This system
was replaced by one devised by C. Kellogg in
1938 that remained in use until 1975, when the
current classification system became the standard
for soil surveys in the United States. In
Canada surveys began later and were initially
patterned on the U.S. system. In 1960 a comprehensive
soil classification system was developed
by Canadian soil scientists to support an
expanded soil survey program throughout the
agricultural areas of the country. This system
was adjusted several times to best fit the soil
properties that the ongoing survey discovered.
In many ways, it is now like that used in Great
Britain.

The earliest soil maps were made using topographic
or plane table maps as base maps.
Air photos became the base maps on which
soil boundaries were placed in the 1930s. They
came into use following the placement of the
soil survey within the Natural Resources Conservation
Service of the U.S. Department of
Agriculture. The Canadian Plains began their
surveys about the time air photos came into
common use. A new generation of soil maps
from these photos combined with more recent
ones were completed for the Canadian
Plains in the early 1990s.

Canadian surveys have followed much the
same trends, especially since the early 1960s.
In both countries, surveys now use new technologies
in remote sensing, global positioning,
and base maps made from digital images.
These maps will become a component of
complete geographic information systems
being developed in the Great Plains.